Using smaller-diameter enhanced tubes, the evaporators cut ammonia charge by 53% compared to units with larger tubes
John Kollasch, Evapco
While Evapco, Taneytown, Md., has garnered considerable attention for its packaged low-charge-ammonia Evapcold units, the company has also been active in developing ammonia evaporators that lower charge in central systems, including two new ones introduced this year that offers its lowest charge to date.
The new evaporators, the SSTSB series and SSTEB low-profile series, both utilize 3/8-inch-diamter internally enhanced stainless steel tubes, which lower the charge compared to 5/8-inch-diameter tube models; their recirculation rate is 1.2:1.
“Smaller diameter tubes equal smaller coil volume, which means lower ammonia charge,” said John Kollasch, Evapco’s vice president, industrial refrigeration product application & marketing for Evapco, in a presentation at the IIAR’s Natural Refrigeration Conference & Heavy Equipment Expo, held earlier this year in San Antonio, Texas. “The driving force of a charge in evaporators is the coil volume.”
“Smaller diameter tubes equal smaller coil volume, which means lower ammonia charge.”
– John Kollasch, Evapco
Evapco’s SST-B evaporators, introduced in 2015, are all certified in accordance with AHRI Standard 420.
Compared to Evapco’s SSTMB evaporator with 5/8-inch-diameter tubes, the SSTSB model uses 53% less ammonia charge (1.19 lbs./TR vs. 2.5 lbs./TR) in a liquid overfeed (both 1.2:1 recirculation rate) example given by Kollasch. In a comparison to a DX system using the SSTMB evaporator with 5/8-inch-diameter tubes, the SSTMB unit uses 45% less ammonia.